[Hawkular-dev] Pozvánka: Discuss Inventory Sync - St 2016/04/20 3:30PM - 4:30PM (Hawkular)

[Lukas Krejci]

The discussion we had revolved mainly about what does sync (or lack thereof) 
mean in the bigger picture of Hawkular.

First, I will summarize the discussion and the main questions we raised 
(please fill in the gaps if you find I forgot about something) and then, in a 
subsequent email, I'll try to provide my answers to those questions to start 
off further discussion.

== Should we delete stuff from inventory when it's not present in the sync 
report?

On one hand, one could argue that yes, we should delete whatever the feed 
doesn't see, because, well, it isn't there and therefore inventory should not
keep it, because then it would not represent what the true state of affairs is 
(this brings forth the missing versioning in inventory - if we had that, we 
would keep the historical record of the resource being there).

On the other hand, users should "see something" when a resource they expect to 
exist suddenly disappears.

Yet another stance on this is that if stuff is kept in inventory even after it 
has stopped being reported by feeds, it should not remain there forever (why 
is the app that I undeployed a month ago still showing up in inventory?).

== What does time since last sync mean?

Say we have an embedded Widfly agent that we haven't heard from for a year. 
Does it mean that there's just nothing new coming from it or it just means 
that the server the agent was running in no longer runs? And more importantly 
what should we do about it?

The idea was to somehow store the time the last sync occurred and base further 
decisions on that.
 
What this timestamp would mean would depend on what we're looking at.
For a feed, this would mean the last time it synced and hence was running 
correctly.
For a resource managed by a feed, this would mean the last time the feed saw 
that resource (provided we don't delete the resources during sync immediately 
upon not seeing them).

For an embedded feed, not seeing it running either means that the server it's 
embedded in is not running or it also can mean that the feed was just 
"removed" from the server it was running in.

For a standalone feed managing remote servers/processes, this would mean the 
feed is not running, but would not tell us anything about the servers it 
manages.

== How do we determine what's "the last time we've seen something live?"

This can be based on the last sync time or the last time we've seen some 
metric associated with a resource or the last time we've seen a (to be 
implemented) availability metric associated with a resource.

== Conclusion

The three questions raised above are intertwined and the answers to them will 
influence each other. Overall these questions revolve around determining 
staleness/age of the inventory data and how to react on it.

On Tuesday, April 19, 2016 06:51:04 PM lkrejci at redhat.com wrote:
> Byli jste pozváni na následující událost.
> 
> Název: Discuss Inventory Sync
> With the first version of the inventory sync (or rather "dump" as it exists 
> at the moment) in inventory, I'd like to invite you to discuss its
> features and future directions so that we make it as useful as possible for
> the feed writers.
> 
> https://bluejeans.com/8169978803
> Kdy: St 2016/04/20 3:30PM - 4:30PM Středoevropský čas - Praha
> Kde: https://bluejeans.com/8169978803
> Kalendář: Hawkular
> Kdo:
>      * lkrejci at redhat.com- autor
>      * jmazzite at redhat.com
>      * jshaughn at redhat.com
>      * hrupp at redhat.com
>      * hawkular-dev at lists.jboss.org
> 
> Podrobnosti o události:  
> https://www.google.com/calendar/event?action=VIEW&eid=cTExdWdzbXR0Z3Y2M2xoMm
> dwbW05bzZyMGMgaGF3a3VsYXItZGV2QGxpc3RzLmpib3NzLm9yZw&tok=NjMjcmVkaGF0LmNvbV9
> mbWlnMm9zdTY5a21hNDdqcmRjMnZlbjRtb0Bncm91cC5jYWxlbmRhci5nb29nbGUuY29tNDk0ZDJ
> mNjE5NjFhZWE3OWRkOThmMDExY2NkMDZkZTU1ZjQ3Zjk4OA&ctz=Europe/Prague&hl=cs
 
> Pozvánka z Kalendáře Google: https://www.google.com/calendar/
> 
> Tento e-mail na účet hawkular-dev at lists.jboss.org jste obdrželi z toho  
> důvodu, že jste účastníkem této události.
> 
> Chcete-li se odhlásit z odběru oznámení o této události, odmítněte událost. 
> Případně si můžete na adrese https://www.google.com/calendar/
> zaregistrovat účet Google a řídit nastavení oznámení pro celý svůj
> kalendář.
> 
> Přeposláním této pozvánky byste mohli komukoli z příjemců umožnit, aby  
> změnil vaši odpověď na toto pozvání. Další informace najdete na  
> https://support.google.com/calendar/answer/37135#forwarding

--

Lukas Krejci